1. Field of the Invention
The present invention is directed to a brake lining wear sensor and is more particularly directed to an erodable parallel array for detecting progressive brake lining wear.
2. Summary of the Prior Art
Various brake lining wear detection systems are known in the art. In addition, temperature measurement systems are known. However, few brake lining monitoring systems combine both wear detection and temperature sensing. One such temperature and wear detection technique monitors the resistance of a temperature sensitive resistor yielding a signal which represents the operating temperature of the brake lining so that extreme temperature conditions can be detected and corrective action taken. Once the electrical conductive loop is worn away, an open circuit is detected which signals the need for lining replacement.
One method to detect brake lining employs an embedded conductive wire loop within the brake lining. When the loop is broken and furthermore, when electrical contact is made between the wire loop and a brake drum surface, lining wear out is detected. Another brake wear and temperature measurement system utilizes a plurality of thermo-responsive elements disposed within the brake lining where each element is selectively monitored to determine if abnormal temperatures have been encountered and/or whether the brake lining has worn to such an extent that one or more of the thermally responsive elements have been broken.
A more traditional brake temperature indication means comprises a thermocouple disposed within the brake lining connected to a display means to indicate operating temperature of the brake lining. A similar technique uses a combination temperature and wear sensor disposed in a brake cylinder where the sensor has a slider mechanism that is pressed on the face of a brake cylinder to indicate brake wear and also includes a temperature sensing device thereby indicating the wear of the brake lining and overheating of the brake fluid through a pair of lead out wires.
It is an object of the present invention to improve upon the drawbacks of the related art devices.
The present invention is directed to a parallel resistor array for progressively detecting brake lining wear. A plurality of conductors are embedded within a brake lining or otherwise disposed between the brake surface and an actuator. Each of the conductors is connected to a resistor that is in turn connected to an indicator circuit. The indicator circuit is also connected to the brake surface. The conductors have progressively increasing lengths extending from the brake surface to the actuator. When the brakes are applied, the brake surface may contact at least one of the conductors to close the indicator circuit. As the brake lining wears, each of the conductors progressively contact the brake surface when the brakes are applied thus progressively adding a resistor to the indicator circuit. The conductors and resistors are arranged in parallel and thus as the brake lining wears, the overall resistance in the indicator circuit progressively decreases. Progressive brake lining wear may then be detected directly corresponding to the change in resistance in the indicator circuit.